In the field of 3GPP that regulates technical standards of the third generation mobile communication system, since the end of 2004, has started researches for Long Term Evolution/System Architecture Evolution (LTE/SAE) techniques to optimize and enhance functions of 3GPP techniques in correspondence to a plurality of forums and new techniques relevant to the 4th generation mobile communication.
The SAE based on the 3GPP SA WG2 relates to a network technique for determining a network structure and supporting mobility of a heterogeneous radio network system with cooperating with an LTE operation of the 3GPP TSG RAN. The SAE, one of the most important standardization issues of the 3GPP, is implemented to develop a 3GPP system into a system that supports various wireless access techniques based on IP (Internet Protocol). More concretely, the SAE has been implemented for an optimized packet-based system capable of minimizing transmission delay with an enhanced data transmission capability.
A conceptual reference model of the SAE, defined by 3GPP SA WG2 includes a non-roaming case, and a roaming case having various scenarios. Details of the conceptual reference model can be referred from TS 23.401 and TS 23.402 which are 3GPP standard documents. This may be schematically reconfigured in FIG. 1.
FIG. 1 is a structural view of an evolved mobile communication network.
One of the most representative characteristics of the network of FIG. 1 is that a structure is based on a two-layer model (2 Tier Model), an evolved NodeB (so-called eNodeB) of an Evolved UTRAN and a Gateway of a Core Network. The eNodeB has similar functions to them of both an RNC and a NodeB of the conventional UMTS system. And, the Gateway has a similar function to it of the conventional SGSN/GGSN.
Another important characteristic of the network is that a Control Plane and a User Plane between an Access Network and a Core Network are interchanged to each other through different interfaces. In the conventional UMTS system, one interface (lu) exists between an RNC and an SGSN. However, since a Mobility Management Entity (MME) which processes a control signal is separated from a Gateway (GW), two interfaces (i.e, S1-MME and S1-U) were respectively used.
FIG. 2 shows an (e)NodeB and a Home (e)NodeB.
In the 3rd or 4rd generation mobile communication system, efforts to increase a cell capacity have been ongoing in order to support high-capacity service such as multimedia contents and streaming, and a bi-directional service.
As various techniques for transmitting a large amount of data in addition to multimedia relating techniques are required, many methods for increasing wireless capacity have been researched. One of the methods include a method for allocating frequency resources as much as possible. However, there have been limitations in allocating limited frequency resources to a plurality of users as much as possible.
In order to increase a cell capacity, there are efforts to use a high frequency bandwidth, but this causes to reduce a cell radius. When cells having a small radius, such as pico cells are used, a frequency bandwidth of the cell can increase highly than that in the conventional cellular system thus to transmit more information. However, in this case, more base stations have to be installed in the same area, which results in high costs.
In order to increase a cell capacity by using a small cell, a femto-base station such as a Home (e)NodeB has been proposed.
Referring to FIG. 2, an (e)NodeB 20 may correspond to a macro-base station, whereas a Home (e)NodeB 30 may correspond to a femto-base station. In the specification, the terms will be explained based on the 3GPP. And, the (e)NodeB 20 will be used so as to indicate ‘NodeB’ or ‘eNodeB’, and the Home (e)NodeB 30 will be used so as to indicate ‘Home NodeB’ or ‘Home eNodeB’.
A cell of the Home (e)NodeB 30 is implemented in an Open Access Mode, a Closed Access Mode, and a Hybrid Access Mode according to an access permission policy.
In the case of the Open Access mode, the cell of the Home (e)NodeB 30 provides service to all serviceable terminals without limitations.
In the case of the Closed Access mode, the cell of the Home (e)NodeB 30 permits access of only allowed terminals.
In UMTS/EPS of the 3GPP standard, it has been proposed that one or more Home (e)NodeBs operated in the Closed Access mode forms one Closed Subscriber Group (CSG). That is, one CSG may be composed of one or more Home (e)NodeBs, and the terminal also receives one permission (e.g., one CSG membership) to access the cells of the Home (e)NodeBs. Here, the terminal may have one or more CSG memberships to access one or more CSGs, and may have time information allowed according to each CSG. Information on accessible CSGs is called as an Allowed CSG List. This allowed CSG list is stored in the terminal, and a network entity such as MME, SGSN, MSC, HSS, and HLR. The Home (e)NodeB may support one or more CSGs.
FIG. 3 is an exemplary view showing a structure of a network including a Home eNodeB.
As shown in FIG. 3A, a core network 50 includes an MME 51, a Serving Gateway (S-GW) 52, an SGSN 56, a Packet Data Network Gateway (P-GW) or a PDN Gateway 53. The core network 50 may further include a PCRF 54 and an HSS 55.
FIG. 3A shows a Home NodeB 31 based on a UMTS Terrestrial Radio Access Network (UTRAN), and a Home eNodeB 32 based on an Evolved-UTRAN (E-UTRAN). The Home NodeB 31 based on a UTRAN is connected to the SGSN 56 through a gateway 35. The Home eNodeB 32 based on an E-UTRAN is connected to the MME 51 and the S-GW 52. Here, a control signal is transmitted to the MME 51, and a user data signal is transmitted to the S-GW 52. The gateway 35 may be disposed between the Home eNodeB 32 based on an E-UTRAN and the MME 51.
FIG. 3B shows an interface of the Home eNodeB 32 based on an E-UTRAN. The Home eNodeB 32 based on an E-UTRAN and the gateway 35 are referred to as a Home eNodeB sub-system. The Home eNodeB 32 based on an E-UTRAN is connected to a UE 10 through an LTE-Uu interface. The Home eNodeB 32 and the MME 51 are connected to each other through an S1-MME interface. The Home eNodeB 32 and the S-GW 52 are connected to each other through an S1-U interface. The S1-MME interface and the S1-U interface may pass through the gateway 35. The MME 51 and the S-GW 52 are connected to each other through an S11 interface. And, the MME 51 and the HSS 55 are connected to each other through an S6a interface.
FIG. 4 is an exemplary view showing an interface between the Home eNodeB 32 and the MME 51 of FIG. 3 as a protocol stack.
As shown in FIG. 4, each of the Home eNodeB 32 and the MME 51 includes a first layer (physical layer), a second layer (media access control layer), a third layer (Internet Protocol (IP) layer), Signaling Control Transmission Protocol (SCTP), and S1 Application Protocol (S1-AP).
The S1-AP is an application layer protocol between the Home eNodeB 32 and the MME 51. The SCTP ensures transmission of a signaling message between the Home eNodeB 32 and the MME 51.
In the related art, when the Home (e)NodeB 30 is operated in a Hybrid Access Mode and the UE 10 requests access to the Home (e)NodeB 30, the Home (e)NodeB 30 is not provided with information about whether the MME 51 has permitted access of the UE 10 to the Home (e)NodeB 30 as a CSG member or a non-CSG member. This may cause the Home (e)NodeB 30 not to know a connection type of the UE 10 thereto, and not to control radio resources.
More concretely, since the Home (e)NodeB 30 is not capable of identifying a connection type of the UE 10, can not be preformed other policies between the CSG member and the non-CSG member, i.e., radio resource controls such as rate control or diversion of establishment connection.